A free online tuner for guitar, bass, ukulele, violin and voice
The Online Tuner listens through your device’s microphone and tells you exactly which note you are playing, how many cents sharp or flat it is, and its frequency in hertz. The big needle swings left when you are flat and right when you are sharp; when it sits in the green zone, you are within five cents — closer than most people can hear.
Choose a preset for standard or drop-D guitar, 4- or 5-string bass, ukulele or violin and the tuner highlights the nearest string while you tune, with a reference tone for each string if you prefer to tune by ear. Switch to chromatic mode to tune any instrument or to check your singing pitch. The A4 reference can be set anywhere from 432 to 446 Hz for baroque ensembles, orchestras that tune to 442, or anyone experimenting with 432 Hz.
Audio is analysed in real time on your device and never recorded or sent anywhere.
How to use the Online Tuner
- Pick your instrument from the Instrument list, or choose Chromatic for anything else.
- Press Start tuner and allow microphone access when the browser asks.
- Play one string at a time, letting it ring. The note name, cents and frequency appear and the nearest string lights up.
- Turn the tuning peg until the needle rests in the green zone. Come up to the note from below for stable tuning.
- Tap any string button to hear a 3-second reference tone if you would rather tune by ear.
Online Tuner features
Accurate pitch detection
A normalised autocorrelation detector (the McLeod pitch method) with parabolic interpolation resolves pitch to better than one cent on a clean note.
Cents needle and frequency readout
See the deviation in cents on a ±50 cent gauge, plus the exact frequency in Hz — useful for intonation work and for setting up a new instrument.
Instrument presets
Guitar standard and drop D, 4- and 5-string bass, ukulele (G C E A) and violin, with the nearest string highlighted as you play.
Reference tones
Each string button plays a synthesised tone at the correct frequency for the chosen A4 reference.
Adjustable A4 reference
Set the concert pitch from 432 to 446 Hz; every string frequency and reading updates instantly.
Raw microphone input
Noise suppression, echo cancellation and auto gain are switched off so sustained instrument notes are not filtered away as “noise”.
Standard tuning frequencies (A4 = 440 Hz)
Every semitone is a frequency ratio of the twelfth root of two (about 1.0595), and a cent is one hundredth of a semitone. The tuner computes cents as 1200 × log₂(f ÷ ftarget). You can explore the maths with the Frequency Converter.
| Instrument | Strings (low to high) | Frequencies (Hz) |
|---|---|---|
| Guitar – standard | E2 A2 D3 G3 B3 E4 | 82.41 · 110.00 · 146.83 · 196.00 · 246.94 · 329.63 |
| Guitar – drop D | D2 A2 D3 G3 B3 E4 | 73.42 · 110.00 · 146.83 · 196.00 · 246.94 · 329.63 |
| Bass – 4 string | E1 A1 D2 G2 | 41.20 · 55.00 · 73.42 · 98.00 |
| Bass – 5 string | B0 E1 A1 D2 G2 | 30.87 · 41.20 · 55.00 · 73.42 · 98.00 |
| Ukulele – re-entrant | G4 C4 E4 A4 | 392.00 · 261.63 · 329.63 · 440.00 |
| Violin | G3 D4 A4 E5 | 196.00 · 293.66 · 440.00 · 659.26 |
Tips for a steady reading
- Play one string at a time and let it ring; mute the others with your palm so their harmonics do not confuse the detector.
- Pluck over the sound hole or neck pickup rather than near the bridge — the tone is rounder and the fundamental stronger.
- For the low bass strings, use the 12th-fret harmonic or play through an amp or audio interface; tiny laptop microphones struggle below 60 Hz.
- Always tune up to the pitch. If you overshoot, drop below the note and come back up so the string sits against the peg tension and holds.
- Replace very old strings — they go false (their harmonics drift) and no tuner can make them sound right.
Which A4 reference should I use?
440 Hz is the ISO 16 international standard and the right choice for almost everyone — recordings, backing tracks and other players all assume it. Many European orchestras tune to 442–443 Hz for a brighter sound, and some German and Austrian orchestras go to 445–446. Baroque groups often use 415 Hz (a semitone below 440), which is outside this tuner’s range because it is handled simply by reading every note a semitone higher. 432 Hz has a following online; it is roughly 32 cents flat of standard and nothing more mysterious than that.
Online Tuner FAQ
Is this guitar tuner free and does it need a download?
Yes, the online tuner is completely free, with no app, account or plug-in required. It works in Chrome, Edge, Firefox and Safari on desktop and mobile.
How accurate is the online tuner?
On a clean, sustained note it resolves pitch to better than one cent. Professional ears generally cannot distinguish differences under about five cents, which is the width of the green zone.
Why does the tuner show a different note from the one I am playing?
Usually another string is ringing, or the note was plucked too hard and its octave harmonic dominated for a moment. Mute the other strings, let the note settle, and read the display after the first half-second.
Can I tune a 7-string guitar, a mandolin or a cello?
Yes — use Chromatic mode. It detects any note from about 50 Hz to 1,500 Hz, which covers everything from a 5-string bass B to the top of a violin.
Does the tuner work without a microphone?
Pitch detection needs a microphone, but the reference tones work without one: tap a string button and tune by ear until the beats between your string and the tone disappear.
What are cents?
A cent is 1/100 of a semitone. Being 10 cents flat means the string is a tenth of the way down to the next semitone. Most people start to hear a mismatch at around 5–6 cents.